Dams help take edge off flooding in regionWith serious flooding on the Sheyenne River, people wonder why water is being released from Lake Ashtabula through Baldhill Dam near Valley City, N.D.
By: Dave Olson, INFORUM
With serious flooding on the Sheyenne River, people wonder why water is being released from Lake Ashtabula through Baldhill Dam near Valley City, N.D.
The short answer is: If water wasn’t released, it would quickly fill the reservoir and spill over the top, creating serious problems down stream.
Here’s some more information about reservoirs and floods from Tim Bertschi, area flood engineer for the U.S. Army Corps of Engineers. Except where quotations are used, his comments have been paraphrased.
Q: What did the Army corps do to prepare for flood season?
A: Lake Ashtabula, which feeds into the Sheyenne River, and Lake Traverse, which feeds the Bois de Sioux River and ultimately the Red River, were drawn down to the lowest levels permitted.
For Ashtabula, that elevation is 1,257 feet. At Lake Traverse, which is controlled by the White Rock Dam, the maximum draw-down elevation is 974 feet.
What levels are the lakes at now, and how much water is being released from them?
Lake Ashtabula at Baldhill Dam is at about 1,264 feet. At 1,271 feet, water begins to flow over the top in an uncontrolled flow.
About 9,000 cubic feet per second is flowing into Ashtabula, and about 6,000 cubic feet per second is being released.
Lake Traverse is at about 979 feet. At 982 feet, water flows over the top of the dam.
Water is flowing into Lake Traverse at a rate of 1,139 feet per second. It is being released at a rate of 1,500 feet per second.
With water so high on the Sheyenne River, why not reduce the outflow?
“You look at Baldhill, and it sounds terrible that we’re putting out 6,000 (cfs). But really, when there’s 10,000-plus coming in, the dam is doing some good. It would be nice if we could be putting out zero, but if we do that, the dam would overtop and we’d have a catastrophe on our hands.”
What is the picture for Lake Traverse and its outflow into the Bois de Sioux and the Red River?
With projections for a second Red River crest at Fargo and Moorhead continuing to diminish, White Rock Dam will continue to release water from Lake Traverse.
“We would prefer to stay ahead and get that (lake) storage back, in case all of a sudden we get a 3-inch thunderstorm.
“If they (cities on the Red River) were teetering on the edge of really having trouble, like we’re seeing on the Sheyenne, we probably would reduce that more.”
What would happen if Baldhill Dam fails?
It would take the water eight to 12 hours to reach Valley City, so there would be time to get people out of harm’s way. But a big part of Valley City would be devastated, with flooding on first floors and above.
Readers can reach Forum reporter Dave Olson at (701) 241-5555